whose responsible

Here is my situation i worked for a bank up until march 6 when i quit to change jobs. I had direct deposit so when i got my check stub it stated i was overpaid a significant amount of money. Now i called th eautomated number to see what the balance was in my account and it stated the same thing. So I let the money sit in there approximately 2 weeks thinking they would discover the mistake and withdraw the funds. When they didn't I withdrew the money. This past Friday I received a letter explaining about the overpayment and it showed what had happened. On the letter it stated I should call the vice-president of payroll to make arrangements for repayment and if I didn't respond by march 31st then they would proceed accordingly. When I called today to discuss my proposed arrangements in a way that i can afford he told me that he has to discuss it with their legal department to see if they agree to those terms. Now my question is if they don't agree what can I do to resolve this matter without it being taken to court? And whose fault was it anyway that the mistake was made because he kind of tried to blame it on me by saying "well we thought that you would've called to tell us about the mistake" now anyone in their right frame of mine would have done the same thing i did, now am i responsibe to pay it back . help me

[This message has been edited by tanisha (edited March 27, 2000).]